This invention relates to apparatus and method for ultrasonic sealing disposable diapers and, more particularly, to sealing with an orbitally movable horn and anvil.
It is known that ultrasonic sealing is commonly used in many applications to weld various types of web materials together. A majority of these applications utilize a stationary mounted ultrasonic member (power supply, converter, booster, horn) in connection with a rotating patterned anvil roll member. The horn is the part of the vibratory or ultrasonic member that comes in contact with the product and effects sealing in combination with the anvil. The vibratory energy is transferred directly to the webs as they pass through these members causing them to melt and bond to each other. This approach, because of its tangential contact time, is limited to speeds and construction that require a minimal seal time.
One current apparatus employs a shuttle mechanism to increase sealing time. The vibratory member clamps down on the web with an anvil member underneath and travels with the web for a predetermined distance where it releases--having sealed a specific area--and returns to the starting point for another cycle. This is a chain drive system with complicated dynamics which makes it difficult to control.
Ultrasonic sealing on the fly has been successful because of the small area that the vibratory member has been required to seal, i.e., tangential contact to the patterned anvil roller. The drawbacks to this system are limited web speed, the product orientation required for a good seal and is limited to putting a good seal only on small areas.
The problem is that many product constructions, such as training pants, require a substantial increase in seal time due to the multiple webs and the increased sealing area. To run these on present systems would require a slower web feed rate making it more costly and changing the orientation of the web or product as it passes.